Exam-style question
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What does a redshift in astronomical spectra indicate?.
- A.The source is moving towards the observer
- B.The source is moving away from the observer
- C.The source is stationary
- D.The observer is moving away from the source
Model answer
What a good answer should say
- The source is moving away from the observer
Explanation
Why this works
A redshift in astronomical spectra indicates that the source of light is moving away from the observer, resulting in longer wavelengths. This phenomenon is a key piece of evidence for the expanding universe theory.
In contrast, a blueshift would indicate that the source is moving towards the observer, leading to shorter wavelengths.
Common mistake
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